A number of academic groups and life sciences companies are developing and testing approaches to delay aging -- the most significant risk factor for the vast majority of serious human diseases. Critical for these efforts is the development and validation of minimally invasive, cost-effective biomarkers of aging. DiamiR, a molecular diagnostics company, has developed proprietary platform technology for early detection and moni- toring of pathophysiological processes in different organs based on analysis of organ-enriched microRNA (miRNA) pairs in plasma. In this SBIR Phase I we propose to use the technology to select effective biomarkers of brain aging. Brain aging is characterized by neurite and synapse dysfunction and loss and neuronal death. A hypothesis being tested in the current proposal is that these processes can be detected in vitro by quantitative (RT-qPCR) analysis of brain-enriched and inflammation-associated miRNAs circulating in the blood. miRNAs enriched in different brain regions (hippocampus, midbrain, cerebellum, cortex, pituitary gland) and present in neurites and synapses, and several inflammation-associated miRNAs will be tested as biomarker candidates. Our previous studies on brain health produced highly promising results: biomarker miRNA pairs selected among brain-enriched miRNAs circulating in plasma were found to detect Mild Cognitive Impairment (MCI) with up to 96% accuracy, predict progression from normal cognition to MCI with 84% accuracy 1-5 years prior to clinical diagnosis, and differentiate Alzheimer's and Parkinson's diseases from age-matched control and from each other with accuracy >85%. In the preliminary study on aging several brain-enriched miRNAs were found to differentiate cognitively normal subjects of two age groups with p < 0.05 to p < 0.001. The current study will be performed using plasma samples prospectively collected at the New York Blood Center. Specific aims include (1) assessing feasibility of the approach and selecting miRNA biomarker pairs effectively differentiating younger (26-35 year-old) from older (56-65 year-old) healthy subjects (20 samples per group); and (2) using sets of miRNA biomarker pairs selected in Aim 1 to evaluate age-related dynamics and gender-dependent differences in plasma samples collected from 26 to 75 year-old healthy subjects (100 samples in total). In Phase II, DiamiR will assemble a knowledgebase by conducting studies with 1,000+ plasma samples collected from 20 to 90 year-old subjects. Further, miRNAs enriched in other than brain organs will be tested as biomarkers of aging of these organs. The generated data will be used to determine age-dependent ranges of concentrations of miRNA biomarker pairs defining normal aging. The long-term goal of the project is to develop sensitive, minimally invasive molecular assays for evaluation and monitoring of aging in the brain and other organs. The assays will be developed as in vitro diagnostics (IVD) and used for monitoring of aging, for assessment of therapeutic regimens and life style changes aimed at delaying (or reversing) normal aging, and for early detection of anomalies characteristic of aging associated diseases.